The present invention relates to an electrophotographic copying machine and, more particularly, to an exposure mode selecting circuit for automatically selecting an automatic exposure control mode for an electrophotographic copying machine.
An electrophotographic copying machine produces an electrostatic latent image on a photoreceptor using an optical system. The latent image corresponds to an image on a copy document such as a manuscript or book to be copied. A developing device is provided so that tone particles are electrically adhered to the latent image, so that the latent image becomes visible as a toner image. The toner image is transferred onto a copy paper via a corona transference charger.
Conventionally, the light exposure of the electrophotographic copying machine is controlled depending on the shade of the copy document to be copied. For this purpose, a manual switch for controlling the light exposure has been provided for a manual exposure control mode. Recently, an improved copying machine has been proposed including an automatic exposure controller for automatically controlling the light exposure, the controller being used for an automatic exposure control mode. In such a case, a mode switch is provided for selecting the manual exposure control mode and the automatic exposure control mode. To select either mode, this switch must be operated. Sometimes, it may be troublesome to have to operate this switch. Further, before the copying operation is started, the operator must check the selection of this mode switch, resulting in an extra task.